Hair Follicles

The outer shield is formed by special keratinocytes. It extends from the opening of the follicle all the way to the dermis. The lowest part of it is the bulb where the hair grows from. In some area the follicles are connected to sebaceous glands, which secret oily substances into the follicles and from there flow to the skin surface.

Like the keratinocytes in the epidermis, those in the follicles also have a growth cycle. When this growth cycle is disturbed, dead keratinocytes are stuck inside the follicles. Together with excessive oily secretion, the follicles are prone to be blocked. This is followed by problems such as pimples, acnes, large pores, uneven skin surface etc.

This explains that blocked follicles are not necessary due to dirtiness. Over zealous cleansing and rubbing will only cause damages to the skin.

Sebaceous Glands

The sebaceous glands in this layer are found at the base of each hair follicle. Normal functioning of the sebaceous glands is essential for healthy skin. They make the special oils called sebum for the skin and hair, providing a natural protection system, which waterproofs the hair and lubricates the skin.

In adolescence when the male hormones surge, they often over-produce the sebum, which leads to the formation of blackheads and pimples.

When the environmental temperature increases, the sebum will flow more. They melt at above
34°C. Therefore in summer the sebum secretion seems to be higher.

Sweat Glands

These can be divided into Eccrine Sweat Glands and Apocrine Sweat Glands.

Eccrine sweat glands are located in the dermis, widely in all parts of the body. There are millions of them. They open into the skin surface and their main function is to excrete sweat and regulate the body temperature. The sweat contains water, salt, urea, and electrolytes. The overall pH value is slightly acidic at about 4 - 5. When we sweat profusely, the pH on the skin will change from this to neutral, thereby increasing the chance of infection by microorganisms.

Apocrine sweat glands are much bigger, and are located only at the underarms and female genitalia. They open into the near top of the follicles. They contain fatty acids which are the source of their odour character. If they are further fermented by microorganisms, the odour will become strong and offensive.